Optical Coupler for Rotating Catheter

ABSTRACT

An optical coupler for coupling to a rotating catheter has a housing with a rotatable distal face and a stationary proximal face. The distal face has an eccentric port and a central port. A lens is disposed inside the housing to intercept a rotating collection beam emerging from the eccentric port and to re-direct the collection beam to a focus proximal to the lens as the collection beam rotates. A beam re-director disposed between the lens and the distal face is oriented to direct a delivery beam toward the central port.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/615,279, filed on Jul. 8, 2003, which is a continuation-in-part ofU.S. patent application Ser. No. 10/309,477, filed on Dec. 4, 2002. Theentire contents of each of the foregoing applications are incorporatedherein by reference.

TECHNICAL FIELD

This invention relates to fiber optic catheters, and more particularlyto catheters that accommodate more than one optical fiber.

BACKGROUND

Vulnerable plaques are lipid filled cavities that form within the wallof a blood vessel. These plaques, when ruptured, can cause massiveclotting in the vessel. The resultant clot can interfere with blood flowto the brain, resulting in a stroke, or with blood flow to the coronaryvessels, resulting in a heart attack.

To locate vulnerable plaques, one inserts a catheter through the lumenof the vessel. The catheter includes a delivery fiber for illuminating aspot on the vessel wall and one or more collection fibers for collectingscattered light from corresponding collection spots on the vessel wall.The delivery fiber, and each of the collection fibers form distinctoptical channels within the catheter. The catheter used for locatingplaques is thus a multi-channel catheter.

In operation, a light source outside the catheter introduces light intothe delivery fiber. A detector, also outside the catheter, detects lightin the collection fiber and generates an electrical signalrepresentative of that light. This signal is then digitized and providedto a processor for analysis.

A vulnerable plaque can be anywhere within the wall of the artery. As aresult, it is desirable to circumferentially scan the illuminated spotand the collection spot around the vessel wall. One way to do this is tospin the multi-channel catheter about its axis. However, since neitherthe light source nor the processor spin with the catheter, it becomesmore difficult to couple light into and out of the delivery andcollection fibers while the catheter is spinning

SUMMARY

The described device, method and system are based on the recognitionthat a lens can be made to focus light onto a fixed point even as thesource of that light moves relative to the lens.

In one aspect, the invention includes an optical coupler having ahousing with a rotatable distal face and a stationary proximal face. Thedistal face has an eccentric port and a central port. A lens is disposedinside the housing to intercept a rotating collection beam emerging fromthe eccentric port and to re-direct the collection beam to a focusproximal to the lens as the collection beam rotates. A beam re-directordisposed between the lens and the distal face is oriented to direct adelivery beam toward the central port.

In some embodiments, the beam re-director is a penta-prism. However,other types of beam re-directors, for example a prism or a mirror, canalso be used.

Certain embodiments also include a light source disposed to direct adelivery beam radially inward to the beam re-director, and/or a detectordisposed at the focus for receiving the rotating collection beam.

In some embodiments, the lens is configured to focus the collection beamon an axis of rotation of the distal face. However, in otherembodiments, the lens is configured to focus the collection beam off anaxis of rotation of the distal face. In yet other embodiments, the lensis an axicon lens.

In another aspect, the invention includes a system for identifyingvulnerable plaque. The system includes a rotating catheter having acollection fiber and a delivery fiber extending therethrough, and ahousing with a rotatable distal face and a stationary proximal face. Thedistal face has an eccentric port and a central port. A lens is disposedinside the housing to intercept a rotating collection beam emerging fromthe eccentric port and to re-direct the collection beam to a focusproximal to the lens as the collection beam rotates. A beam re-directordisposed between the lens and the distal face is oriented to direct adelivery beam toward the central port.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entirety. In case of conflict, the presentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

Embodiments of the invention may have one or more of the followingadvantages. By providing a continuous connection to both optical fibers,the rotary coupler permits the entire circumference of an artery to bescanned automatically.

A rotary coupler having the features of the invention can also be usedto identify other structures outside but near a lumen, or on the surfaceof the lumen wall. For example cancerous growths within polyps can beidentified by a catheter circumferentially scanning the lumen wall ofthe large intestine, cancerous tissue in the prostate may be identifiedby a catheter scanning the lumen wall of the urethra in the vicinity ofthe prostate gland, or Barrett's cells can be identified on the wall ofthe esophagus. In addition to its medical applications, the rotarycoupler can be used in industrial applications to identify otherwiseinaccessible structures outside pipes.

Other features and advantages of the invention will be apparent from thefollowing detailed description, and from the claims.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a system for identifying vulnerable plaque in a patient.

FIG. 2 is a cross-section of the multi-channel catheter in FIG. 1.

FIG. 3 is a profile view of the multi-channel coupler of FIG. 1.

FIG. 4 is an end view of the multi-channel coupler of FIG. 1.

FIG. 5 is the same profile view of FIG. 3 with the core rotated 180degrees.

FIG. 6 is a profile view of the multi-channel coupler incorporatingadditional fibers.

FIGS. 7-8 are embodiments that include a delivery beam re-director.

FIG. 9 is a penta-prism for use as a beam-redirector in the embodimentsof FIGS. 7-8.

FIG. 10 is a schematic view of a path traced by a collection beam on alens.

FIG. 11 is a schematic view of a catheter core whose axis of rotation isoffset from the axis of the lens.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION System Overview

FIG. 1 shows a diagnostic system 10 for identifying vulnerable plaque 12in an arterial wall 14 of a patient. The diagnostic system features acatheter 16 to be inserted into a selected artery, e. g. a coronaryartery, of the patient. A delivery fiber 18 and a collection fiber 20extend between a distal end 21 and a proximal end 23 of the catheter 16.

As shown in FIG. 2, the catheter 16 includes a jacket 17 surrounding arotatable core 19. The delivery fiber 18 extends along the center of thecore 19 and the collection fiber 20 extends parallel to, but radiallydisplaced from, the delivery fiber 18. The rotatable core 19 spins atrate between approximately 4 revolutions per second and 30 revolutionsper second.

Referring again to FIG. 1, at the distal end 21 of the catheter 16, atip assembly 22 directs light traveling axially on the delivery fiber 18toward an illumination spot 24 on the arterial wall 14. The tip assembly22 also collects light from a collection spot 26 on the arterial wall 14and directs that light into the collection fiber 20.

A multi-channel coupler 28, which is driven by a motor 30, engages theproximal end 23 of the catheter 16. The motor 30 spins the catheter 16,enabling the diagnostic system 10 to circumferentially scan the arterialwall 14 with the illumination spot 24.

The multi-channel coupler 28 guides a beam from a laser 32 (or othersource, such as an LED, a super luminescent LED, or an arc lamp) intothe delivery fiber 18 and guides light emerging from the collectionfiber 20 into one or more detectors 66. The multi-channel coupler 28performs these tasks while the catheter core 19 continuously spins.

The detectors provide an electrical signal indicative of light intensityto an amplifier 36 connected to an analog-to-digital (“A/D”) converter38. The A/D converter 38 converts this signal into data that can beanalyzed by a processor 40 to identify the presence of a vulnerableplaque 12 hidden beneath the arterial wall 14.

Coupler Rotary Junction to Catheter

A multi-channel coupler 28 for carrying out the foregoing tasks, asshown in FIG. 3, includes a cylindrical housing 42 having a proximalface 44 joined to a distal face 46 by a peripheral wall 48. The distalface 46 rotates with the catheter core 19, whereas the proximal face 44and the remainder of the housing 42 remain stationary.

The distal face 46 of the housing 42 has a catheter core port 53 forreceiving the catheter core 19, a central port 52 for receiving thedelivery fiber 18, and an eccentric port 54 for receiving the collectionfiber 20. The central port 52 is located at the intersection of an axisof rotation 50 with the distal face 46. The eccentric port 54 isradially displaced from the central port 52. As a result, when thecatheter core 19 spins about the axis 50, the delivery fiber 18 remainsstationary and the collection fiber 20 traces out a circular path, asshown in an end view in FIG. 4. Bearings 96 at the central port 52,eccentric port 54, and catheter core port 53 couple the housing 42 tothe catheter core 19. The bearings 96 also enable the catheter core 19to spin about the axis of rotation 50 that intersects the proximal anddistal faces 44, 46 of the housing 42.

The distal face 46 of the housing 42 is rotatably coupled to thecatheter 16. Two optical fibers extend through the catheter 16: adelivery fiber 18 for illuminating the arterial wall 14 and a collectionfiber 20 that collects light scattered from the arterial wall 14. Thecatheter core 19 spins about the axis 50 while the housing 42 remainsstationary.

A laser 32 directed towards the distal face 46 produces a delivery beam58 centered on the axis 50 as shown in FIG. 3. A first collimating lens62 collimates the delivery beam 58 and directs it through the housing 42and through an aperture 94 of a rotation-to-stationary (R-S) lens 92.The R-S lens aperture 94 is a circular opening that is centered on theaxis 50 and has a diameter slightly larger than the delivery beam 58. Afirst optical relay 64 within the housing 42 then receives thecollimated delivery beam 58 and directs it distally across the housing42 toward the central port 52, where it enters the delivery fiber 18. Asused herein, an optical relay refers to a set of optical elements, suchas lenses, prisms, and mirrors, arranged to direct light from a sourceto a destination.

In FIG. 3, this first optical relay 64 includes a converging lensfocused at the central port 52. However, the first optical relay 64 caninclude components other than, or in addition to that shown in FIG. 3.Between the proximal face 44 and the central port 52, the delivery beam58 is not constrained to travel along the axis 50 as shown in FIG. 3.The delivery beam 58 may travel on any path that leads to the deliveryfiber 18. One design option, shown in FIG. 7, includes locating thelaser 32 or directing the delivery beam 58 to start between the R-S lens92 and the distal face 46. This would eliminate the need for the R-Slens aperture 94.

In the embodiment of FIG. 7, the light source 32 directs the deliverybeam 58 radially toward a centrally mounted beam re-director 51. Thebeam re-director 51, which can be a prism, (including a penta-prism), ora mirror, re-directs the delivery beam 58 along the axis 50, toward thedistal face 46. A first optical relay 64, disposed to intercept thedelivery beam 58 on its way to the distal face 46, directs the deliverybeam 58 into the delivery fiber 18.

A second optical relay 70 receives a collection beam 68 from theeccentric port 54 and directs it along a circular path that traverses aperipheral portion of the lens 92. The lens 92 brings the collectionbeam 68 to a focus at a detector 66, which generates an electricalsignal in response thereto. This electrical signal is provided to theamplifier 36.

In FIG. 7, the detector 66 is disposed at a point offset from the axis50. However, the lens 62 and the path traced by the collection beam 68can be configured to direct the collection beam 68 toward the axis 50,as shown in FIG. 8. When this is the case, the detector 66 is placed onthe axis 50, as shown in FIG. 8. A beam re-director 51 in the form of apenta-prism 98, shown in FIG. 9, is particularly useful because an inputbeam 100 incident on a penta-prism 98 always emerges as an output beam102 orthogonal to the input beam 100. This property of a penta-prism 98reduces the need for precision alignment.

The collection beam 67 is divided into a proximal side extending fromthe detector 66 to the R-S lens 92 and a distal side 67 extending fromthe R-S lens 92 to the eccentric port 54. A second optical relay 70receives the collection beam 68 from the eccentric port 54 and directsit to the R-S lens 92. The R-S lens 92 directs the collection beam 68 tothe detector 66 located towards the proximal face 44. The second opticalrelay 70 and the distal side of the collection beam 67 rotate circularlyabout the axis 50 and trace a circular path on the R-S lens 92. Withoutitself moving, the R-S lens 92 continuously redirects the collectionbeam 68 onto the stationary detector 66.

In FIG. 5, the second optical relay 70 and the distal side of thecollection beam 67 have rotated 180 degrees from the position depictedin FIG. 3. The R-S lens 92 directs the distal side of the collectionbeam 67, now located 180 degrees from its position in FIG. 3, back tothe stationary detector 66 regardless of where the proximal side of thecollection beam 67 intersects the R-S lens 92. The R-S lens 92continuously directs the collection beam 68 onto the stationary detector66 as the rotation of the core causes the optical relay and the distalside of the collection beam 67 to traverse a circular path on the R-Slens 92.

In one embodiment, the geometry or grading index of the R-S lens 92 isnot symmetric about the axis 50. Instead, the geometry or grading indexof the R-S lens 92 varies as a function of angle. For example, theportion of the lens through which the collection beam 68 passes in FIG.3 refracts the collection beam 68 less than the portion of the lensthrough which the collection beam 68 passes in FIG. 5. As a result, theR-S lens 92 redirects the distal side of the collection beam 67 to thestationary detector 66 even as the proximal side of the collection beam67 traces a circular path on R-S lens 92. The R-S lens 92 can include avariety of optical elements, such as lenses, prisms, and mirrors,arranged to direct light from a rotating source to a fixed destination.A central portion of the lens can be removed or made transparent toallow the delivery beam 58 to pass unaltered. A peripheral portion ofthe R-S lens 92 can be reduced to only the portion of the lens throughwhich the collection beam 68 passes, thereby forming a donut shapedlens. This donut shaped lens would reduce the material needed to producethe R-S lens 92.

In another embodiment, the R-S lens 92 is symmetric about the axis 50,however the center of a circular path 104 traced out by the collectionbeam 68 is offset from the axis 50, as shown in FIG. 10. This can beachieved, for example, by offsetting the lens 92 relative to thecatheter core 19 as shown in FIG. 11. Note that in this embodiment, aswell as in the embodiment of FIG. 3, the collection beam 68 traverses apath through portions of a 92 lens having different opticalcharacteristics, the difference being that in FIG. 3, the lens 92 isradially asymmetric and the axis of rotation 50 is coincident with thecenter of the lens 92, whereas in FIG. 7, the lens 92 is radiallysymmetric, but the axis of rotation 50 is offset from the center of thelens.

In another embodiment, the R-S lens 92 is an axicon lens, also known asa conical lens, or a rotationally symmetric prism. Such lenses cause thecollection beam 68 to pass through the same location regardless of theangle of the collection fiber 20 and to do so without focusing thecollection beam 68.

OTHER EMBODIMENTS

The optical couplers shown in FIGS. 1-5 are two-channel couplers. Eachhas a delivery channel that carries the delivery beam 58 and acollection channel for carrying a collection beam 68. However,additional collection or delivery channels can be added by providingadditional collection ports or delivery ports, each of which is incommunication with an additional collection fiber or delivery fiber.

In the embodiment of FIG. 6, an additional eccentric port 55 and opticalrelay 71 are provided in the distal face 46. The collection beams 68 and72 emerging from the apertures and relays form concentric nested traceson the R-S lens 92. The R-S lens 92 then directs these traces to theirperspective stationary detectors 66 and 69. Analogous to the depictionand discussion of FIGS. 3 and 5, the R-S lens continuously directs thecollection beams 68 and 72 onto the stationary detectors 66 and 69 asthe optical relays 70 and 71 and the distal side of the collection beamsrotate from 0 to 360 degrees in a circular path. This embodiment is notlimited to a single additional collection beam. The embodiment wouldinclude the capacity to handle a plurality of additional collectionfibers. In addition, the embodiment is not limited to only additionalcollection fibers. Additional delivery fibers could also be present.

All lenses and optical relays referred to herein are shown as having asingle optical element. However, each of these structures can includetwo or more optical elements in optical communication with each other.

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

1. An optical coupler comprising: a housing with a rotatable distal faceand a stationary proximal face, the distal face having an eccentric portand a central port; a lens disposed inside the housing to intercept arotating collection beam emerging from the eccentric port and tore-direct the collection beam to a focus proximal to the lens as thecollection beam rotates; and a beam re-director disposed between thelens and the distal face, the beam re-director being oriented to directa delivery beam toward the central port.